Natural Docs - Natural Docs is an open-source documentation generator for multiple programming languages.
ROBODoc - Supports C, C++, Fortran, Perl, shell scripts, Assembler, DCL, DB/C, Tcl/Tk, Forth, Lisp, COBOL, Occam, Basic, HTML, Clarion, and any other language that supports remarks.
Doxygen - Generate documentation from source code
TypeDoc - A documentation generator for TypeScript projects
ClickHelp - Create, translate, and publish technical documentation easily in one portal, anywhere in the world!
Apiary - Collaborative design, instant API mock, generated documentation, integrated code samples, debugging and automated testing